Micro-Structured Crystalline Radiation Detectors

ABSTRACT

In one aspect, a radiation detector is disclosed, which includes a substrate having a plurality of microcapillary channels, and a crystalline scintillator material disposed in said channels so as to generate a plurality of independent radiation sensing elements associated with each channel for detecting incident radiation and generating an optical radiation in response to the detection of the incident radiation. In some embodiments, the incident radiation can include any of alpha (α), beta (β), gamma (γ), X-ray and neutrons.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.17/864,091 filed on Jul. 13, 2022, which claims priority to ProvisionalPatent Application No. 63/221,235 filed on Jul. 13, 2021, entitled“Micro-structured Crystalline Radiation Detectors,” the content of whichis herein incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure is generally directed to radiation detectors, andin particular to such radiation detectors that employ a plurality ofmicrocapillary structures having scintillator or semiconductorradiation-detecting materials to detect incident radiation.

BACKGROUND

The present application relates generally to radiation detectors andmethods for their fabrication, where the radiation detectors can beutilized to detect a variety of ionizing and non-ionizing radiation.

X-ray imaging is a widely-used diagnostic technique that spans numerousfields. X-rays interact with atomic electrons resulting in higherabsorption cross-sections for higher atomic number elements depending onthe overall electron density distribution of the object. X-rayradiography is currently performed primarily using direct and indirecttechniques, which involve the detection of charge carriers and photonsgenerated by the X-rays, respectively. Indirect flat panel X-ray imagers(FPXIs) with scintillating layers (such as commercially availablemicro-columnar CsI and Gd₂O₂S) have high detection quantum efficiency(DQE) and are the preferred detectors for all hard X-ray imagingapplications. These sensors, however, provide poor spatial resolutionsand suffer from low detection sensitivity.

Direct detectors can be used to achieve a higher spatial resolution butcharge trapping and defects typically result in a significant reductionof their sensitivity. Due to their lower atomic numbers, large areadirect detectors such as a-Se and Si detectors have low efficiencies forthe detection of higher X-ray energies.

Accordingly, there is a need for radiation detectors that exhibit both ahigh spatial resolution as well as a high detection efficiency.

SUMMARY

In one aspect, a radiation detector is disclosed, which includes aplurality of microcapillary structures, and a scintillator materialassociated with each microcapillary structure so as to generate aplurality of independent radiation sensing elements each associated withone of the microcapillary structures for detecting incident radiationand generating scintillation radiation in response to the detection ofthe incident radiation. Each of the microcapillary structures can be inthe form of a channel that is at least partially (and typically fully)filled with the scintillator material.

In some embodiments, the incident radiation can include any of alpha(α), beta (β), gamma (γ), X-ray and neutrons.

In some embodiments, the scintillator material can have a singlecrystalline composition (structure) or a polycrystalline composition(structure). In other embodiments, the scintillator material can have anamorphous composition (structure).

A variety of scintillator materials can be used in a radiation detectoraccording to the present teachings. By way of example, in someembodiments, the scintillator material includes any of an organic andinorganic scintillator material. In some such embodiments, thescintillator material can include an organic-inorganic hybridscintillator material. Some examples of such organic-inorganic hybridscintillator materials include, without limitation, any of OD, 1D, 2D,or 3D perovskite material. By way of example, the perovskite materialcan be PEALPB.

Some examples of inorganic scintillator materials suitable for use in aradiation detector according to the present teachings can include,without limitation, Cs₃Cu₅I₅, CsI, and CLLB.

In some embodiments, the scintillator material can be an oxidescintillator. Some examples of such oxide scintillators can include, forexample, any of BGO and Gd₂O₂S.

In some embodiments, the scintillator material can include a halidescintillator material. Some examples of such a halide scintillatormaterial can include, without limitation, an inorganic, an organic andhybrid organic-inorganic scintillator material.

In some embodiments, the microcapillary structures are formed within asubstrate. In some embodiments, the substrate can be formed of any ofglass and quartz. In some embodiments, the substrate can be formed of ametal, such as lead (Pb) and tungsten (W). In some embodiments, thesubstrate can be formed of a polymeric material. By way of example, andwithout limitation, the polymeric material can be a scintillating or anon-scintillating plastic material. By way of example, in someembodiments, the plastic material can be PTFE (polytetrafluoroethylene).In some embodiments, the substrate can be formed of a scintillating PVTplastic. By way of example, the scintillator material of which thesubstrate is formed can be suitable for the detection of a radiationmodality different than the radiation modality that can be detected viathe scintillator material associated with the microcapillary structures.

In some embodiments in which the substrate is formed of a scintillatormaterial, the scintillator material of which the substrate is formed canbe different from the scintillator material associated with themicrocapillary structures. By way of example, and without limitation,the substrate can be formed of a scintillator material that is suitablefor detection of one radiation modality (e.g., X-rays) while thescintillator material in the microcapillary channels of themicrocapillary structures can be suitable for the detection of adifferent radiation modality (e.g., neutrons).

Some examples of such scintillator materials suitable for use in formingthe substrate can include, without limitation, LYSO:Ce or PWO. In someembodiments, the substrate can include a ceramic scintillator. Someexamples of a ceramic scintillator material can include, withoutlimitation, any of LuAG:Ce or YAP:Ce.

In some embodiments in which the substrate is formed of a scintillatormaterial, such a scintillator material can have any of a singlecrystalline, a polycrystalline or an amorphous structure.

As noted above, in some embodiments, the scintillator material in themicrocapillary structures or the scintillator material from which thesubstrate is formed can have any of a single crystalline structure, apolycrystalline structure, or a combination of a single crystalline anda polycrystalline structure. For example, the scintillator materialassociated with at least one of the microcapillary structures (typicallyall of the microcapillary structures) can have a single crystallinecomposition. In some embodiments, the scintillator material associatedwith at least one of the microcapillary structures (typically all of themicrocapillary structures) can have a polycrystalline composition. Insome embodiments, the scintillator material associated with at least oneof the microcapillary structures (typically all of the microcapillarystructures) can have a mixed single and poly- crystalline composition.

In some embodiments, the scintillator material that is associated witheach of the radiation sensing elements can have a thickness in a rangeof about 20 microns to about 5 centimeters, e.g., in a range of about 50microns to about 1 millimeter, or in a range of about 10 millimeters toabout 1 cm. Further, in such embodiments, the scintillator material canhave a maximum transverse dimension in a range of about 1 micron toabout 3 mm, e.g., in a range of about 10 microns to about 1 mm, or in arange of about 50 microns to about 200 microns.

In some embodiments, at least one of the microcapillary structuresextends across an entire thickness of the substrate from a proximal endthereof to a distal end (herein also referred to as first and secondends). In some embodiments, the scintillation radiation generated inresponse to the detection of incident radiation can exit themicrocapillary structures through any of its proximal and distal ends.

In some embodiments, the microcapillary structures are formed aschannels filled entirely with the scintillator material. In otherembodiments, at least some of the microcapillary channels may be onlypartially filled with the scintillator material.

In some embodiments, a radiation detector according to the presentteachings can exhibit a modulation transfer function (MTF) of at least5% for spatial frequencies in a range of zero and about 8 1p/mm fordetection of X-ray radiation. In some embodiments, a radiation detectoraccording to the present teachings can exhibit a modulation transferfunction (MTF) of at least 5% for spatial frequencies in a range of zeroand about 8 1p/mm for detection of gamma-ray radiation. In someembodiments, a radiation detector according to the present teachings canexhibit a modulation transfer function (MTF) of at least 5% for spatialfrequencies in a range of zero and about 8 1p/mm for detection ofneutrons. In some embodiments in which the radiation detector exhibitsMTF values in the above ranges, the scintillator material associatedwith each of the radiation-detecting elements can have a maximumtransverse dimension in a range of about 1 micron to about 200 microns.

In some embodiments, the substrate of a radiation detector according tothe present teachings can include, e.g., be formed of, a material thatexhibits an index of refraction that is greater than an index ofrefraction of the scintillator material at the frequency of thescintillation radiation such that the scintillation radiation generatedin each of the radiation sensing elements is substantially trappedwithin that sensing element via internal reflections at interfacesbetween the scintillator material and the substrate material.

In some embodiments, at least one of the microcapillary channelsassociated with one of the microcapillary structures includes a coatinglayer covering at least a portion of an inner surface thereof forenhancing optical isolation between said at least one channel and anadjacent channel. In some such embodiments, the coating layer can becapable of absorbing the scintillation radiation that is generated bythe scintillator material in response to the detection of the incidentradiation. By way of example, and without limitation, the coating layercan include any of a metal and a metal oxide. By way of example, thecoating layer can include (e.g., be formed of) any of gold, silver,MgO₂, BaSO₄, and Al₂O₃. As discussed in more detail below, in someembodiments, the coating layer can absorb the scintillation radiation(or at least a portion thereof) and emit radiation at a longerwavelength.

In some embodiments, the radiation detector can include a supportsubstrate to which a substrate in which the microcapillary structuresare formed is coupled. In some embodiments, such a support substrate caninclude (e.g., be formed of) any of semiconductor and glass. In someembodiments, the support substrate can include a fiber optic plate. Byway of example, the fiber optic plate can include any of glass and apolymer. In some embodiments, the microcapillary structures can be inthe form of free-standing structures that are held together via suitablemeans, e.g., optical glue or epoxy, PMMA (polymethylmethacrylate), whichcan form a light guide, among others.

In some embodiments, at least one of the microcapillary structuresincludes a coating layer covering at least a portion of an inner surfacethereof for enhancing optical isolation between that microcapillarystructure and an adjacent one. In some such embodiments, the coatinglayer can be a reflecting layer that reflects the scintillationradiation back into the scintillator material of the microcapillarystructure. In some embodiments, the coating layer can be formed of metalor a metal oxide layer. By way of example, the metal layer can be formedof gold or silver. Some examples of suitable oxide coating materials caninclude, without limitation, any of MgO₂, BaSO₄, and Al₂O₃

In some embodiments, at least one of the microcapillary structures caninclude an inner insulting layer and an outer reflective layer disposedon an inner surface thereof.

In some embodiments, the coating layer can be an absorbing layer thatcan absorb the scintillation radiation and emit radiation at a longerwavelength.

In some embodiments, at least two of the microcapillary structuresinclude two different scintillator materials. The two scintillatormaterials can be suitable for detecting two different radiationmodalities. By way of example, one of the radiation modalities caninclude any of X-ray and γ radiation and the other radiation modalitycan include neutrons. In some embodiments, the two differentscintillator materials may be selected to allow detection of radiationin two different energy regimes. In some such embodiments, an opticalimager that is optically coupled to the radiation detector can generateradiation image data that can be processed to generate a mixed image ofthe different radiation modalities. In other words, one portion of theimage can correspond to one of the radiation modalities and anotherportion of the image can correspond to another radiation modality.

In some embodiments, one or more of the radiation sensing elements caninclude a high-Z matrix scintillator that can provide informationregarding the energy of the detected γ rays and one or more of the otherradiation sensing elements can include a low-Z matrix scintillator, butultrafast scintillator material, that can provide information regardingthe timing of the detection of the gamma radiation. As an example, thehigh-Z matrix scintillator can provide the gamma energy information,while the low-Z but ultrafast scintillator can provide timinginformation regarding the detection of the incident radiation.

In a related aspect, a radiation detector is disclosed, which includes aplurality of radiation sensing elements, where each of the radiationsensing elements includes a hollow microcapillary channel, and ascintillator material filling at least a portion of the inner lumen ofsaid microcapillary channel. Each of the radiation sensing elements isconfigured to receive incoming radiation such that at least a portion ofthe incoming radiation is incident on the scintillator material, whichgenerates scintillation radiation in response to detection of theradiation.

The microcapillary structures can include an inlet and an outletaperture through at least one of which the scintillation radiation canbe collected from the microcapillary structure.

In some embodiments, the radiation detector can further include asupporting substrate to which the plurality of radiation sensingelements are coupled. In some embodiments, the microcapillary structurescan be formed within a substrate (e.g., by forming microcapillarychannels within the substrate and at least partially filling thosechannels). In some embodiments, the microcapillary structures can be inthe form of free- standing structures that are held together viasuitable means, e.g., optical glue, epoxy, or a polymer that istransparent to the scintillation light.

In some embodiments, the microcapillary structures can have a length ina range of about 20 microns to about 5 centimeters, e.g., in a range ofabout 50 microns to about 1 millimeter, or in a range of about 10millimeters to about 1 centimeter, or any other subrange encompassed bythe range of about 20 microns to about 5 centimeters. Further, themicrocapillary channels can have a maximum transverse dimension (e.g., adiameter in case of cylindrical microcapillary channels) equal to orless than about 3000 microns, e.g., in a range of about 10 microns toabout 200 microns.

In some embodiments, the radiation sensing elements are distributed asmultiple stacked layers. In some such embodiments, the radiation sensingelements within one layer are configured for preferential detection ofone radiation modality and the radiation sensing elements within anotherlayer are configured for preferential detection of another radiationmodality. For example, the radiation sensing elements within one layercan detect X-ray or γ radiation and the radiation sensing elementswithin another layer can detect neutrons.

In a related aspect, an imaging system is disclosed, which includes aradiation detector for generating scintillation radiation in response tothe detection of an incoming radiation and an optical imager that iscoupled to the radiation detector so as to receive the scintillationradiation to generate image data corresponding to the detectedradiation. The radiation detector can be any of the radiation detectorsdescribed herein. By way of example, the radiation detector can includea substrate supporting a plurality of microcapillary channels, and ascintillator material that at least partially fills the microcapillarychannels so as to generate a plurality of independent radiation sensingelements associated with each microcapillary channel for detectingincident radiation and generating scintillation radiation in response tothe detection of the incident radiation.

In some embodiments, the optical imager includes a plurality of imagingpixels each optically coupled to one of the radiation sensing elementsto receive the scintillation radiation generated by that sensing elementand generate one or more imaging signal(s) in response to detection ofthe scintillation radiation. The imaging system includes a circuitryelectrically connected to the optical imager to process the imagingsignals generated by the optical imager and process the imaging signalsto generate an image of the incident radiation. In some embodiments, theoptical imager can include an array of photon-counting energy-sensitivephotodetectors. By way of example, such photodetectors include siliconphotomultipliers (SiPMs) and photomultiplier tubes (PMTs). Examples ofhigh spatial resolution SiPMs include linearly graded SiPM arraysavailable from FBK. Examples of high spatial resolution PMTs includemulti-anode PMTs manufactured by Hamamatsu Photonics of Japan.

In a related aspect, a radiation detector is disclosed, which includes aplurality of microcapillary channels, and a semiconductor materialfilling (at least partially) said channels so as to generate a pluralityof independent radiation sensing elements each of which is associatedwith one of the channels for detecting incident radiation via generationof electrical charges (electron-hole pairs). The semiconductor materialcan partially, or fully, fill the microcapillary channels.

Each of the microcapillary channels includes a plurality of electrodesfor collecting the electron-hole pairs for generating one or moreelectric signals (e.g., an electric current) in response to detection ofthe incident radiation. By way of example, in some embodiments, each ofthe electrodes includes an electrically conductive layer (e.g., ametallic layer) that at least partially coats a top and a bottom surface(e.g., top and bottom ends) of the semiconductor material associatedwith a radiation sensing element so as to be in electrical contact withthe semiconductor material. In some embodiments, an inner surface of arespective one of the channels can be coated with a cathode and an anodeelectrode (which electrodes are electrically insulated from one another)such that the electrodes are in electrical contact with thesemiconductor material.

In some embodiments, at least one of the microcapillary channelsincludes an electrically insulating coating layer that covers at least aportion of an inner surface thereof. By way of example, such aninsulating coating layer can function as a passivating layer helpingreduce the dark current associated with the semiconductor material. Insome embodiments, the coating layer can include (e.g., be formed of) anoxide material, such as silicon oxide. In some embodiments, at least oneof the microcapillary channels can have an inner passivating layer(e.g., an inner silicon oxide layer) and an outer electricallyconductive layer (e.g., a gold layer) coating an inner surface thereof.

In some embodiments, the semiconductor material can have any of asingle- or a poly-crystalline structure. In some embodiments, thesemiconductor material can have an amorphous structure.

By way of example and without limitation, the substrate material caninclude any of glass, a polymer and a ceramic material, among others.

Any suitable semiconductor material can be employed for forming theradiation detector. Some examples of suitable semiconductor materialsinclude, without limitation, silicon (Si), germanium (Ge), GaAs, amongothers.

In some embodiments, each of the microcapillary channels can include anaperture through which the incident radiation can reach thesemiconductor material. Such an aperture can be positioned at one orboth ends or between the two ends along the microcapillary structures.In some embodiments, incident radiation can penetrate through the wallsof the microcapillary structures to reach the semiconductor material. Insome embodiments, the charge-collecting electrodes are coupled to theproximal and the distal ends of the semiconductor material to generateelectrical signals in response to the detection of the incidentradiation.

In some embodiments, each of the microcapillary channels includes a pairof electrodes each in the form of an electrically conductive layercoating a portion of the inner surface of the microcapillary channel,e.g., extending between two opposed ends of the microcapillary channel.The two conductive electrodes can be insulated from one another so as toallow one of them to function as a cathode electrode and the other oneto function as an anode electrode. By way of example, the conductivecoating can be formed of a metal, such as gold or silver.

In some embodiments, at least one, and typically all of themicrocapillary channels, are entirely filled with the semiconductormaterial. In some embodiments, one or more of the microcapillarychannels may be only partially filled with the semiconductor material.

In some embodiments, the radiation detector exhibits a modulationtransfer function (MTF) of at least 5% for detection of incidentradiation, e.g., radiation in the visible portion or infrared portion ofthe electromagnetic spectrum, at a spatial frequency in a range of zeroand about 8 1p/mm.

In a related aspect, a radiation detector is disclosed, which includes aplurality of radiation sensing elements each comprising: a hollowmicrocapillary channel, and a semiconductor filling at least partially alumen of the microcapillary channel, where each of the radiation sensingelements is configured to receive incident radiation such that at leasta portion of the incident radiation is received by the semiconductormaterial, which generates one or more electrical signals in response tothe detection, and generally proportional to the energy, of the receivedincident radiation.

In some embodiments, each of the microcapillary channels includes a pairof electrodes for collecting electron-hole pairs generated in thesemiconductor material associated with that microcapillary structure inresponse to detection of the incident radiation.

In some embodiments, the radiation detector can further include asupporting substrate to which said plurality of radiation sensingelements are coupled.

In a related aspect, a radiation detector is disclosed, which includes aplurality of microcapillary structures, wherein said microcapillarystructures are at least partially filled with a radiation detectingmaterial so as to provide a plurality of independent radiation sensingelements such that each of the radiation sensing elements is associatedwith one of said microcapillary structures for detecting incidentradiation and generating one or more signals in response to thedetection of the incident radiation. In some embodiments, the radiationdetecting material can have any of a single- and poly-crystallinestructure. In some embodiments, the radiation detecting material canhave an amorphous structure.

In some embodiments, the radiation detecting material can include afirst scintillator material that is configured to generate scintillationradiation in response to detection of the incident radiation. By way ofexample, the incident radiation can be any of α, β, γ, X-ray andneutrons.

In some embodiments, the scintillator material can include any of anorganic, an inorganic and an organic-inorganic hybrid scintillatormaterial. By way of example, the organic-inorganic hybrid scintillatormaterial comprises any of OD, 1D, 2D or 3D perovskite material.

In some embodiments, the microcapillary structures are formed in asubstrate. In some such embodiments, the substrate can include (e.g., beformed of) a second scintillator material. The first and the secondscintillator materials can be different. For example, the first and thesecond scintillator materials can be suitable for the detection ofdifferent radiation modalities and/or the detection of radiation indifferent energy regimes.

In some embodiments, the substrate can include a material exhibiting anindex of refraction greater than an index of refraction of thescintillator material at a frequency associated with the scintillationradiation such that the scintillation radiation generated in each ofsaid sensing elements is substantially trapped within that sensingelement via internal reflections at interfaces between said scintillatormaterial and said substrate material.

In some embodiments, at least one of the channels can include a coatinglayer covering at least a portion of an inner surface thereof forenhancing photon generation in response to the incoming radiation andenhancing optical isolation between said at least one channel and anadjacent channel. An example of such a coating layer includes ⁶LiF.

In some embodiments, at least one of the microcapillary structures caninclude a wavelength shifting material coating at least a portion of aninternal surface thereof.

In some embodiments, the plurality of microcapillary structures caninclude at least two subsets having different scintillator materials.

In some embodiments, the plurality of radiation sensing elements aredistributed in two or more stacked layers. In some such embodiments, theradiation sensing elements associated with at least two of said layersinclude different scintillator materials.

In some embodiment, an optical imager is coupled to said independentradiation sensing elements to receive the scintillation radiation togenerate an image corresponding to the incident radiation. By way ofexample, the image can exhibit a modulation transfer function (MTF) ofat least 5% for a spatial frequency in a range of zero to about 8 1p/mmfor detection of the incident radiation.

In some embodiments, the radiation detecting material can include asemiconductor material, wherein said semiconductor material isconfigured to generate electric charges in response to detection of theincident radiation. Each of the microcapillary structures can include aplurality of electrodes for collecting the electric charges generated bythe semiconductor in response to detection of the incident radiation.The plurality of electrodes associated with each of said microcapillarystructures can include an anode electrode and a cathode electrodeelectrically coupled to opposed ends of the microcapillary structure.

In some embodiments, the plurality of electrodes can include anelectrically conductive layer coating at least a portion of an innersurface of a respective one of said microcapillary structures and beingin electrical contact with the semiconductor material associated withthat microcapillary structure.

In some embodiments, at least one of said microcapillary structures caninclude a passivating, electrically insulating layer coating at least aportion of an inner surface thereof for reducing dark current associatedwith the semiconductor material.

In some embodiments, at least one of the microcapillary structures caninclude an inner electrically insulating layer and an outer electricallyconductive layer coating at least a portion of an inner surface thereof.

In some embodiments, the microcapillary structures are formed in asubstrate. By way of example, and without limitation, the substrate caninclude any of glass, polymer, ceramic, metal or semiconductor material.

By way of example and without limitation, the semiconductor material caninclude any of silicon, Germanium (Ge), Cadmium Zinc Telluride (CdZnTe),Cadmium Telluride (CdTe), Mercuric iodide (HgI₂), Bismuth Triiodide(BiI₃), Thallium Bromide (TIBr), and Hybrid Perovskites such as CesiumLead Bromide (CsPbBr₃), Methylammonium Lead Bromide (MAPbBr₃),Methylammonium Lead Iodide (MAPbI₃), Formamidinium Methylammonium CesiumLead Bromo-iodide (FAMACs).

The radiation detector can include a detection and analysis circuitrythat is electrically coupled to said radiation detecting elements forreceiving the electrical signals generated by the electrodes of saidradiation detecting elements and analyzing the electrical signals togenerate an image of the incident radiation.

In some embodiments, the radiation detector and said detection andanalysis circuitry are configured such that said image exhibits amodulation transfer function (MTF) of at least 5% for a spatialfrequency in a range of zero to about 8 1p/mm for detection of saidincident radiation. By way of example, in some such embodiments, themaximum transverse dimension of the microcapillary structures can be ina range of about 10 microns to about 200 microns.

In another aspect, a method of making a radiation detector is disclosed,which includes dispersing one or more precursor materials including aradiation-detecting material or a precursor thereof into a plurality ofmicrocapillary channels formed in a substrate; and processing theprecursor materials to cause formation of a plurality of independentradiation sensing elements each associated with one of themicrocapillary channels. In some embodiments, the microcapillarychannels can have a maximum transverse dimension less than about 3000microns, e.g., in a range of about 10 microns to about 3000 microns,such as in a range of about 20 microns to about 1000 microns, or in arange of about 50 microns to about 500 microns or in a range of about100 microns to about 200 microns, and a length in a range of about 20microns to about 5 centimeters, such as in a range of about 100 micronsto about 3 cm, e.g., in a range of about 500 microns to about 2 cm, orin a range of about 1 mm to about 4 cm.

In some embodiments, each of the crystalline radiation-sensing elementsincludes a single crystalline structure. In some embodiments, at leastone of the crystalline radiation-sensing elements includes apolycrystalline structure. In some embodiments, at least one of thecrystalline radiation-sensing elements includes a mixture of a singleand a polycrystalline structure.

In some embodiments, the step of dispersing the one or more precursormaterials into the microcapillary channels includes introducing a liquidcontaining the one or more precursor materials into the microcapillarychannels. The liquid can be introduced into the microcapillary channelsvia any of drop casting, dip coating, full or partial dipping, spraying,and ink jet printing.

In some embodiments, the liquid is introduced into the microcapillarychannels via a capillary action. In some embodiments, the introductionof the liquid into the microcapillary channels includes drop casting theliquid into the microcapillary channels at a slanted substrateorientation. By way of example, the substrate can be slanted at an anglein a range of about 10° to about 45°.

In some embodiments, the radiation-detecting material can include atleast one of a scintillator material and a semiconductor material. Byway of example, and without limitation, the scintillator material can bePEALPB.

In some embodiments, the processing of the one or more precursormaterials to cause crystallization thereof can include using one or moreof: solvent evaporation, antisolvent-assisted crystallization, inversetemperature crystallization, vertical gradient temperature freezing,horizontal gradient temperature freezing, heat exchanger method growth,gas-assisted crystal growth, thermal quenching, and polymerization.

In some embodiments, the step of dispersing the one or more precursormaterials into the microcapillary channels comprises introducing aliquid containing said one or more precursor materials into saidmicrocapillary channels. The liquid is introduced into themicrocapillary channels via any of drop casting, dip coating, full orpartial dipping, spraying, and ink jet printing. In some embodiments,the liquid is introduced into the microcapillary channels via acapillary action. In some embodiments, the liquid is introduced into themicrocapillary channels via drop casting the liquid into themicrocapillary channels at a slanted substrate orientation.

In some embodiments in which the microcapillary structures are formed inthe substrate, the liquid is introduced into the substrate by placingthe substrate at a slanted angle relative to a source of liquid. By wayof example, the angle can be in a range of about 10° to about 45°.

In some embodiments, the radiation-detecting material includes at leastone of a scintillator material and a semiconductor material. A varietyof scintillator and semiconductor materials, including those describedherein, can be employed for fabricating a radiation detector accordingto the present teachings. By way of example, the scintillator materialcan include

PEALPB. By way of example, the semiconductor can include any of silicon,germanium, and GaAs.

In some embodiments, the step of processing the one or more precursormaterials comprises causing crystallization thereof using at least oneof the following techniques: solvent evaporation, antisolvent-assistedcrystallization, inverse temperature crystallization, vertical gradienttemperature freezing, horizontal gradient temperature freezing, heatexchanger method growth, gas-assisted crystal growth, thermal quenching,and polymerization.

The processing step can include using a solution-based technique tocause crystallization of the precursor materials. The processing stepcan include using directional evaporation of a solvent containing theprecursor materials to cause crystallization of the precursor materials,where the directional evaporation of the solvent is facilitated bychanging any of temperature of the precursor materials and a pressure towhich the solvent is exposed.

In some embodiments, the processing step includes usingantisolvent-assisted crystallization of the precursor materials. Theantisolvent can be introduced into the microcapillary channels at a rateand a volume suitable for initiating and sustaining crystallization ofthe precursor materials in the microcapillary channels. In someembodiments, the antisolvent can be introduced into the microcapillarychannels at a rate and a volume suitable for initiating and sustainingcrystallization of the precursor materials in the microcapillarychannels. In some embodiments, the processing step can include usinginverse temperature crystallization to cause crystallization of theprecursor materials. In some embodiments, the processing step caninclude using a polymerization technique for causing crystallization ofthe precursor materials.

In some embodiments, the processing step can include using a melt-basedtechnique for causing crystallization of the precursor materials. Insome embodiments, the processing step includes using directionalgradient temperature freezing for causing crystallization of theprecursor materials. In some embodiments, the processing step caninclude using a heat exchange growth method for causing crystallizationof the precursor materials. In some embodiments, the processing stepincludes using a gas-assisted crystal growth technique to causecrystallization of the precursor materials. In some embodiments, theprocessing step includes using thermal quenching to causecrystallization of the precursor materials.

In some embodiments, the processing step includes using physical vapordeposition for growing the radiation sensing materials in themicrocapillary channels.

In some embodiments, the processing step includes using thermalevaporation to cause formation of the radiation detecting materials inthe microcapillary channels. In some embodiments, the processing stepincludes using a sputtering technique to cause formation of theradiation detecting materials in the microcapillary channels. In someembodiments, the processing step includes using atomic layer depositionfor forming the radiation detecting materials in the microcapillarychannels. In some embodiments, the processing step includes usingchemical vapor deposition for forming the radiation detecting materialsin the microcapillary channels.

In some embodiments, the maximum transverse dimension of themicrocapillary structures can be in a range of approximately 1 μmthrough 3 mm, e.g., in a range of about 1 μm to about 1 mm, or in arange of about 10 μm to about 200 μm.

Further understanding of various aspects of the present teachings can beobtained by reference to the following detailed description inconjunction with the associated drawings, which are described brieflybelow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A schematically depicts a radiation detector according to anembodiment of the present teachings in which a scintillator material isemployed for detecting incoming radiation,

FIG. 1B is a schematic perspective view of a sensing module utilized inthe radiation detector illustrated in FIG. 1A,

FIG. 1C is an end view of a sensing module utilized in the radiationdetector illustrated in FIG. 1A, further schematically illustrating ascintillator material filling the lumen of the sensing module,

FIG. 1D schematically depicts a sensing module having a non-uniformcross-sectional shape characterized by a conical end,

FIG. 2 schematically depicts a radiation detector according to anembodiment in which a plurality of radiation sensing modules aresupported by a supporting substrate,

FIG. 3 schematically depicts that a light ray generated by ascintillator material of a sensing module can undergo multiplereflections at the peripheral surfaces of the sensing module to beguided to at least one end of the sensing module for detection via anoptical imager that is optically coupled to that end,

FIG. 4A is a schematic view of a radiation detector system according toan embodiment of the present teachings in which the sensing modules areoptically coupled to an optical imager, which is configured to detectthe light generated by the scintillator material in response todetection of incoming radiation,

FIG. 4B is a schematic view of a radiation detector system according toan embodiment of the present teachings in which multiple optical imagesare optically coupled to multiple facets of a radiation detectoraccording to the present teachings for detecting scintillation radiationgenerated by the scintillator material of the radiation detector,

FIG. 5A is a schematic axial view of a sensing module, furtherillustrating an electrical conductive coating, e.g., a metal coating,formed on an inner surface of the sensing module,

FIG. 5B is a schematic axial view of a sensing module, furtherillustrating an inner insulating layer and an outer conductive layercoating an inner surface of the sensing module,

FIG. 5C is a schematic axial view of a sensing module, furtherillustrating a wavelength-shifting material formed on an inner surfaceof the sensing module,

FIG. 6A is a schematic view of a radiation detector according to anembodiment of the present teachings, which includes a plurality ofstacked layers of capillary structures,

FIG. 6B is a schematic view of a radiation detector according to anembodiment of the present teachings, which includes two subsets ofmicrocapillary structures filled with different scintillator materials,

FIG. 6C is a schematic view of a radiation detector according to anembodiment of the present teachings, which includes two subsets ofmicrocapillary structures filled with different scintillator materials,where the microcapillary structures of the two subsets are arranged incheckerboard pattern relative to one another,

FIG. 7A is a schematic view of a radiation detector according to anembodiment, which includes a plurality of microcapillary structuresfilled with a semiconductor material,

FIG. 7B is a schematic perspective view of a sensing module employed inthe radiation detector of FIG. 7A,

FIG. 7C is an end axial view of a sensing module utilized in theradiation detector of FIG. 7A, schematically illustrating asemiconductor material disposed in the microcapillary structure of thesensing module,

FIG. 7D schematically depicts a pair of conductive electrodes disposedin a sensing module utilized in the radiation detector of FIG. 7A forcollecting electric charges generated in the semiconductor material inresponse to detection of incident radiation,

FIG. 7E schematically depicts a radiation detector having two subsets ofradiation detecting elements, where the radiation detecting material inone subset differs from the radiation detecting material in the othersubset,

FIG. 8A and 8B schematically illustrate, respectively, a perspective anda cross-sectional view of a radiation detecting element in which an SiO2layer is coated on an inner surface of the microcapillary channelassociated with the radiation detecting element,

FIG. 8C and 8D schematically illustrate a perspective view and across-sectional view of a radiation detecting element in which an innerinsulating layer and an outer conductive layer are deposited on an innersurface of a microcapillary structure associated with that radiationdetecting element,

FIG. 9 is a flow chart listing various steps in a method according to anembodiment for fabricating

FIGS. 10A —10C schematically depict fabrication of an example of a dualimaging detector by introducing a solution containing PEALPB (FIG. 9A)into a plurality microcapillary channels (FIG. 9B) and causing thecrystallization of the PEALPB to generate a single-crystalline PEALPBscintillators (FIG. 9C),

FIGS. 11A-11C show the simulation results generated using Geant 4software of borosilicate glass faceplate with 100 μm hexagonalcapillaries filled with PEALPB similar to the microcapillary platesshown in FIGS. 10A-10C, where FIG. 10A shows a top view of 2×2 cmfaceplate on top of a silicon imager, FIG. 10B shows the side view ofthe model, and FIG. 10C shows a higher magnification of the 1.2 mm tallPEALPB scintillators in a glass matrix,

FIGS. 12A-12B show hit counts of optical photons incident on pixels of asilicon imager generated using a circular pattern of incident 100,000hard X-rays (32 keV) on the array of PEALPB detectors, where FIG. 12Ashows light generation without a microcapillary plate and FIG. 12B showsthe same with the microcapillary plate,

FIG. 13 schematically depicts the architecture of an imager that wasemployed for simulating performance of an embodiment of a radiationdetector according to the present teachings for detection of neutrons,

FIG. 14 shows the calculated number of photons collected by the imagershown in FIG. 13 after firing fast neutrons with an energy of 2.5 MeV atthe imager,

FIGS. 15A and 15B show the neutron detection simulation results,

FIGS. 16 and 17 show the number of neuron detector counts for aplurality of detector channels, illustrating that the simulated neutrondetection performance of detectors according to embodiments of thepresent teachings exceed the respective performance of commercialsensors,

FIG. 18A and 18B show a prototype imager according to an embodiment ofthe present teachings under UV irradiation, where the imager wasconstructed by coupling a PEALPB detector according to an embodiment ofthe present teachings to a CMOS sensor,

FIG. 19 shows a background X-ray image of the PEALPB camera obtained inabsence of an imaging object positioned between an X-ray source and theimager,

FIG. 20A shows X-ray resolution target images using Timepix camera withSi sensor, and FIG. 20B shows X-ray resolution target images usingPEALPB camera,

FIGS. 21A and 21B show X-ray images of a mini-USB drive circuit,

FIG. 22 shows the MTF versus spatial frequency plot derived from thePEALPB camera shown in FIG. 19 , and

FIG. 23 shows the MTF plot for a microcapillary-based detector withextramural absorption layers.

DETAILED DESCRIPTION

The present disclosure relates to radiation detectors for detectingelectromagnetic and/or particle radiation, which can generate light orelectric charge in response to the detection of the incident radiation,as well as radiation detecting systems in which such radiation detectorsare incorporated. By way of example, the radiation detectors accordingto the present teachings can be employed to detect α-, β-, γ-, X-rays,and neutrons, or other ionizing or non-ionizing radiation.

As discussed in more detail below, in some embodiments, such a radiationdetector can employ a scintillator material or a semiconductor materialto generate light or electric charge, respectively, in response todetection of incident radiation. In embodiments, such a radiationdetector can include a matrix of microcapillaries (herein also referredto as microcapillary structures) in which a radiation sensing material(herein also referred to as a radiation detecting material) is disposed,that is, the microcapillaries are partially or fully filled with theradiation sensing material. By way of example, in some embodiments, theradiation sensing material disposed in the microcapillaries can be inthe form of a single crystal. In other embodiments, the radiationsensing material can have a polycrystalline or an amorphous composition.In some embodiments, all of the microcapillary structures can includethe same radiation-detecting material while in other embodimentsdifferent subsets of the microcapillary structures can include differentradiation-detecting materials.

The cross-sectional size of the microcapillaries (e.g., a maximumtransverse size in a plane perpendicular to the longitudinal axis of themicrocapillaries) can be typically in a range of about 1 micrometer(micron) to about 3 millimeters. In embodiments, the use of suchmicrocapillaries can allow the detectors to exhibit a high spatialresolution. In particular, in many embodiments, the present disclosureprovides highly scalable non-hygroscopic detectors that demonstrate anexcellent spatial resolution. For example, in some embodiments, thespatial resolution of a radiation detector according to the presentteachings can be comparable to or better than that of direct X-raydetectors.

The radiation detectors according to the present teachings can beemployed in a variety of different applications including medical andindustrial imaging, homeland security, materials research, among others.By way of example, the microcapillary-structured radiation detectorsaccording to the present teachings can be employed to fabricatelow-cost, large-area ultrahigh spatial resolution high frame rateimagers.

In some embodiments, the spatial resolution of a radiation detector canbe characterized by its modulation transfer function (MTF). As known inthe art, an MTF provides a quantitative measure of the spatial frequencyresponse of an imaging system. In some embodiments, a radiation detectoraccording to the present teachings can exhibit an MTF of at least about5%, e.g., in a range of about 5% to about 100%, for spatial frequenciesin a range of zero to about 8 1p/mm (line pairs per millimeter) fordetection of any of X-ray, gamma-ray radiation, or neutrons. As usedherein, the term MTF when used in connection with a scintillatorradiation detector is intended to refer to the combined MTF of theradiation detector and an optical imager (e.g., CMOS or CCD opticalimager) that is optically coupled to the radiation detector to receiveand detect the scintillation radiation, where the optical imagerexhibits a pixel pitch of at least about 5 microns. As used herein, theterm MTF when used in connection with a semiconductor radiation detectoris intended to refer to the MTF of an image obtained using thesemiconductor radiation detector and electronic circuitry employed toprocess electrical signal(s) generated by the semiconductor detector toform the image.

Spatial resolution is an important factor for X-ray imaging fordistinguishing between two adjacent features in an image. By way ofexample, a detector with a high MTF can reliably detect a micron-scalecancerous lesion or a millimeter-scale fracture in a gas pipeline withhigh levels of confidence. While the trend of the imaging industry isshifting towards feature recognition using artificial intelligence,higher spatial resolutions in radiography images can significantlyenhance the detection probabilities of subtle features such as pulmonarynodules using the neural network deep learning models.

In addition to spatial resolution, the indirect detectors must providehigh enough contrast, be manufacturable in large areas (>10 cm×10 cm),have a fast decay time, and have a low afterglow.

Various terms are used herein consistent with their ordinary meanings inthe art unless specifically modified or further explained herein. By wayof further explanation, the term “microcapillary,” or “microcapillarystructure,” refers to a material structure that extends between aproximal end and a distal end along a longitudinal axis and has amaximum size in a transverse dimension (i.e., a direction that isorthogonal to the longitudinal axis) that is equal to or less than about3 mm, e.g., in a range of about 1 micron to about 1 mm, such as in arange of about 10 microns to about 200 microns, or in a range of about200 microns to about 500 microns, or in a range of about 500 microns toabout 1 mm. The term “microcapillary channel” as used herein refers to amaterial structure providing an inner lumen that can be filled at leastpartially with a radiation-detecting material to form a microcapillarystructure.

A microcapillary channel extends from a proximal to a distal end and hasa maximum size in a transverse dimension (i.e., a dimension that isorthogonal to the longitudinal axis, e.g., assuming that thelongitudinal axis extends along the Z-axis of a Cartesian coordinatesystem, the transverse dimension will be in a plane perpendicular to theZ-axis, such as X- or Y-axis) that is equal to or less than about 3 mm,e.g., in a range of about 1 micron to about 1 mm, such as in a range ofabout 10 microns to about 200 microns, or in a range of about 200microns to about 500 microns, or in a range of about 500 microns toabout 1 mm. A microcapillary structure refers to such a microcapillarychannel whose lumen has been at least partially filed with aradiation-detecting material (e.g., a scintillator material or asemiconductor material).

The terms “single crystal,” or “single crystalline structure,” or“single crystalline composition” are used herein interchangeably torefer to a solid material that can be characterized by a crystal latticethat includes at most three crystal grains, and more preferably only asingle crystal gain with no grain boundaries, such that the crystallattice is continuous and unbroken over the entire, or least over morethan 50% or more than 60%, or more than 70% of more than 80% or morethan 90%, of the volume of the solid material.

The terms “polycrystal,” or “polycrystalline structure,” or“polycrystalline composition” are used herein interchangeably to referto a solid material that is composed of a plurality of single crystaldomains that are randomly oriented relative to one another, where thenumber of crystal domains exceed three.

The term “amorphous” as used herein refers t.) any noncrystalline solidin which the atoms and/or molecules of the solid are not organized in adefinite:lattice pattern. An example of an amorphous solid is glass.

The term “scintillator material” refers to a material that can providedetectable photons in the visible range of the electromagnetic spectrumfollowing passage of incident radiation, as that term is describedherein, through the material. The term “scintillation radiation” refersto the photons in the visible range provided by the scintillatormaterial.

The term “optical radiation” refers to radiation in the wavelength rangeof about 200 nm to about 750 nm.

The term “about” as used herein to modify a numerical value is intendedto indicate a variation of at most 10%, or at most 5% around thatnumerical value. The term “substantially” as used herein is intended toindicate a deviation, if any, of at most 10%, or at most 5%, relative toa complete state and/or condition.

As discussed in more detail below, in some embodiments, the radiationdetecting material employed in a radiation detector according to thepresent teachings can be a scintillator material in which an ionizingphoton (e.g., an X-ray or y-ray) or a particle (e.g., neutron) impingingon the scintillator material creates scintillation radiation in the formof a number of photons (e.g., optical photons) through differentmechanisms, such as band-to-band excitation and relaxation, activatormediated scintillation, self-strapped exciton (STE) scintillation, boundexciton, defect-generated scintillation, among others).

In some embodiments, the radiation detecting material employed in aradiation detector according to the present teachings can be asemiconductor material (herein also referred to as a semiconductingmaterial) in which impinging radiation creates electron-hole pairs thatmove under the influence of an applied electric field towards an anodeand a cathode, respectively, (the holes move towards the cathode and theelectrons move towards the anode) to be collected, thereby generatingone or more electric signals indicative of the detected radiation. Theradiation detectors disclosed herein can detect and measure continuousradiation as well as pulsed radiation, e.g., sub-picosecond radiationpulses, among others.

In some embodiments, a radiation detector according to the presentteachings provides an excellent solution for high spatial resolutionX-ray radiography. In some such embodiments, the detector can include asolution-processable two-dimensional (2D) hybrid perovskitesingle-crystal scintillator, lithium-alloyed phenethylammonium leadbromide (PEALPB) incorporated into a glass microcapillary array. Interms of crystal structure, hybrid (containing organic and inorganicconstituents) perovskite scintillators can be classified asthree-dimensional (3D) and two-dimensional (2D). Although the 3Dperovskite scintillators with lower exciton binding energy (tens of meV)have been shown to provide excellent X-ray scintillator response, the 2Dperovskite scintillators have the potential for providing higher lightyield and faster decay due to their higher exciton binding energy(hundreds of meV).

The 3D lead halide perovskites can be transformed into a 2D one byintroducing a long alkyl chain or a bulky organic cation. PEALPB belongsto the 2D family, where the alternating inorganic/organic layerseffectively confine the exciton inside the inorganic layer generatingscintillation radiation in response to X-rays, fast neutrons, and aparticles that are released as a byproduct of thermal neutron absorptionby Li.

Li-doping provides a unique benefit for perovskite materials. Eventhough the solution-processed hybrid perovskites have demonstratedexcellent performance in many applications, a high concentration of trapstates with a density of 10¹⁵-10¹⁶ cm⁻³ still exists, resulting innonradiative recombination. It has been experimentally verified thatthis deleterious feature can be significantly reduced when the latticeis doped with high concentrations of Li.

It is possible to synthesize the 2D scintillators with highconcentrations of ⁶Li due to the small size of the Li-ion relative tothe large unit cell of 2D materials. Li-alloying also broadens theradioluminescence emission spectra of PEALPB, with its maximum at 436nm. Li-doping also substantially increases the light yield of the PEALPBscintillators.

As discussed further in the Examples section below, the light yield offree-standing single-crystal PEALPB sensors according to certainembodiments was found to be around 18700±1200 ph/MeV as measured using¹³⁷Cs gamma source. The data demonstrates that radiation detectorsaccording to embodiments of the present teachings can provide a highdetection efficiency for radiation imaging applications.

In addition, the presence of ⁶Li provides a large capture cross-sectionfor the detection of thermal neutrons, while the high concentration ofhydrogen (24 hydrogen atoms/molecules) enables the detection of fastneutrons. Thus, by adjusting the content of ⁶Li in the matrix, thesedetectors can also be tuned to detect neutrons over a wide range ofenergies. Accordingly, the present teachings regarding radiationdetectors are also applicable to detectors that are suited for thedetection of neutrons.

With reference to FIGS. 1A, 1B and 1C, a radiation detector 100according to an embodiment of the present teachings includes a pluralityof radiation sensing modules 102 (herein also referred to as radiationsensing elements or simply sensing elements or sensing modules) that arearranged relative to one another to collectively form the radiationdetector 100 for detecting incident radiation. Each sensing module 102includes a microcapillary structure 104 that extends from a proximal end(PE) to a distal end (DE) along a longitudinal axis (LA). The proximaland distal ends can provide apertures 104 a and 104 b. As discussed inmore detail below, in some embodiments, the proximal and distalapertures 104 a/104 b allow collecting light (scintillation radiation)or electric charges generated by a radiation detecting materialassociated with the microcapillary structure 104 in response todetection of incident radiation.

In this embodiment, each microcapillary structure 104 includes aperipheral wall 106 that encloses an inner lumen 108. The term “innerlumen” is used herein to refer to the empty space that is circumscribedby the peripheral wall 106 of a microcapillary structure. The innerlumen 108 is partially (and typically completely) filled with aradiation sensing material 110. While in this embodiment the radiationsensing material substantially fills the entire inner lumen of themicrocapillary channel of a microcapillary structure (i.e., itsubstantially fills the entire volume of the inner space of themicrocapillary structure from its proximal end to its distal end), inother embodiments the radiation sensing material may partially fill theinner lumen of the microcapillary structure. In this embodiment, theperipheral wall 106 of the microcapillary structure includes six facetsthat are positioned at an angle relative to one another such that themicrocapillary structure exhibits a hexagonal cross-sectional shape in aplane perpendicular to its longitudinal axis.

The peripheral wall 106 can be formed of any suitable material. By wayof example and without limitation, the peripheral wall 106 of themicrocapillaries can be formed of a polymeric material, such as plasticmaterials, e.g., PTFE (polytetrafluoroethylene). In other embodiments,the peripheral wall can be formed of a metal such as, Pb or W. In yetother embodiments, the peripheral wall can be formed of glass or quartz.

In some embodiments, the peripheral wall 106 of one or moremicrocapillary structures can itself be formed of a radiation-detectingmaterial, e.g., a scintillator material or a semiconductor material. Insome embodiments, the microcapillary structures are formed in asubstrate as a plurality of channels that are filled at least partiallywith the radiation-detecting material and the substrate itself is formedof a radiation-detecting material (e.g., a scintillator material or asemiconductor material). By way of example, the substrate can be formedof a material that is more suitable for the detection of a radiationmodality different than the radiation modality that is preferentiallydetected by the scintillator material associated with themicrocapillaries. For example, the microcapillaries can be filled withan X-ray sensitive scintillator material and the substrate can be formedof a neutron sensitive scintillator material.

In some embodiments, the incident radiation can reach a radiationdetecting material of a microcapillary structure of a radiation sensingmodule via passage through at least one of the peripheral wall 106, theproximal and the distal apertures 104 a/104 b or a combination of theperipheral wall and one or more of the proximal and the distalapertures.

As shown in FIG. 2 , in some embodiments the microcapillary structures100 are supported by an underlying substrate 200 (herein also referredto as a supporting substrate). In some such embodiments, themicrocapillary structures and the supporting substrate form a unitarystructure. By way of example and without limitation, in someembodiments, such a unitary structure can be formed via generatingchannels (holes) (e.g., via drilling, etching, or otherwise) in a solidsubstrate such that each channel extends from a top surface of thesubstrate towards a bottom surface thereof without reaching the bottomsurface. In other embodiments, the microcapillary structures and thesupporting substrate may be formed as two separate units that areattached to one another, e.g., via optical glue, epoxy, or a polymerthat is transparent to the scintillation light.

As discussed further below, in embodiments in which the radiationsensing material is a scintillator material, the faceted peripheral wallof the microcapillary structure can be effective in channeling the lightgenerated by the scintillator material in response to the detection ofincident radiation along the length of the microcapillary structure,e.g., via total internal reflections at the facets of the peripheralwall.

In this embodiment, the radiation sensing material associated with themicrocapillary structure 104 is a scintillator material that cangenerate light in response to the detection of incident radiation, e.g.,in response to the detection of α-, (3-, γ- radiation, X-rays, andneutrons.

A variety of scintillator materials may be employed in the practice ofthe present teachings. By way of example, and without limitation, thescintillator material may include an organic or inorganic scintillatormaterial. In some embodiments, the scintillator material can include anorganic-inorganic hybrid scintillator material. By way of example, sucha hybrid organic-inorganic scintillator material can be any of OD, 1D,2D, or 3D perovskite material. In some embodiments, the perovskitematerial can include PEALPB. In some embodiments, an inorganicscintillator material includes at least one of Cs₃Cu₅I₅, CsI and CLLB.

In some embodiments, the scintillator material can include an oxidescintillator. In some such embodiments, the oxide scintillator materialincludes any of BGO and Gd₂O₂S. In some embodiments, the scintillatormaterial includes a halide scintillator material. In some suchembodiments, the halide scintillator material includes any of aninorganic, an organic and a hybrid halide scintillator material. In yetother embodiments, the scintillator material can be a plasticscintillator (such as flour-doped PVT). In other embodiments, thescintillator material can be a ceramic scintillator, such as, LuAG:Ce orYAP:Ce. In other embodiments, the scintillator material can be a glassscintillator, such a Li-glass or an organic glass scintillator.

In this embodiment, the scintillator material in the lumen of each ofthe microcapillary structures has a single crystalline structure. Thesingle crystalline structure of the scintillators accurately preservesthe energy deposition information from the radiation interaction,thereby providing the desired high energy resolution. In addition, thesingle crystal scintillators have lower light scattering and providevery high light yield and fast timing response as required by a varietyof applications. As an example, the single crystalline PEALPB exhibits adecay time of 11-24 ns and can be used for applications where timing isimportant such as Time of Flight positron Emission Tomography imaging.

Further, in some embodiments, the microcapillary structures includesingle crystalline scintillator material such that the crystalline axesof the scintillator materials associated with different microcapillarystructures are substantially parallel.

In some embodiments, each of the microcapillary structures has a maximumtransverse dimension (i.e., a maximum size in a cross-sectional planeperpendicular to the longitudinal axis (LA) of the microcapillarystructure) that is equal to or less than about 3 mm, e.g., in a range ofabout 20 microns to about 200 microns. With reference to FIG. 1C, by wayof example, in this embodiment in which the microcapillary structureshave a hexagonal cross-sectional profile, the maximum transverse size isdepicted by reference numeral MTS. In some embodiments, the transversecross-sectional area of each of the microcapillary channels can besubstantially uniform along the length of the microcapillary channel,while in other embodiments, the transverse cross-sectional area may varyalong the length of the microcapillary channel.

By way of example, with reference to FIG. 1D, a microcapillary channel104′ can have a narrowed distal or proximal section, which is in theform of a closed pointed conical end 104′a. As discussed in more detailbelow, such a closed pointed conical end can help with crystallizationof precursor materials in the process of forming the radiation detectingelements, e.g., facilitating the nucleation process.

Further, in some embodiments, each microcapillary structure can have alength in a range of about 20 microns to about 5 centimeters (cm), e.g.,in a range of about 100 microns to about 4 cm, or in a range of about200 microns to about 3 cm, or in a range of about 300 microns to about 2cm, or any other sub-range between about 20 microns to about 5 cm. Inembodiments, such as the present embodiment in which themicrocapillaries are fully filled with the scintillator material, thelength of a microcapillary structure corresponds to the thickness of thescintillator material. Thus, in some embodiments, the thickness of thescintillator material of each microcapillary structure can also be inthe above ranges.

As shown schematically in FIG. 3 , in use, radiation incident on theradiation detector 100 can enter one or more of the radiation sensingmodules (herein also referred to as radiation sensing elements) viatheir respective peripheral walls and/or any of their proximal anddistal apertures to interact with the scintillator material of themicrocapillary structure(s) associated with those sensing modules. Inresponse to the detection of the incident radiation, the scintillatormaterial generates light that can propagate along the length of themicrocapillary structure to exit the microcapillary structure via thedistal end thereof (alternatively, in some embodiments, the generatedlight may be collected via the proximal end of the microcapillarystructure). The propagation of the scintillation light along themicrocapillary structure is facilitated via its reflections at theinternal surfaces of the facets of the peripheral wall of themicrocapillary structure. Further, in some embodiments, themicrocapillary structures can include a coating deposited on innersurfaces thereof, which can also facilitate reflection of thescintillation radiation. Some examples of such reflective coatingmaterials can include thin metal layers, oxide layers, Teflon, or anyother suitable reflecting material.

By way of example, as shown schematically in FIG. 3 , the scintillationlight generated by the scintillator material can undergo multiple totalinternal reflections at the inner surfaces of these facets to be guidedto the distal end (and/or the proximal end) of the microcapillarystructure through which the scintillation light can exit the respectivemicrocapillary structure. In some embodiments, the reflection of thelight at the internal surfaces of the facets of the wall of amicrocapillary can inhibit the passage of the generated light from onemicrocapillary to an adjacent microcapillary resulting in an enhancementof the spatial resolution of the radiation detector. By way of example,in some embodiments, the leakage of the light between adjacentmicrocapillary structures, which is herein also referred to aspixel-to-pixel leakage as in some embodiments the light generated ineach microcapillary structure contributes to the generation of a pixelof an image formed by an optical imager that is optically coupled to theradiation detector, can be less than about 5%, or less than about 2%, orless than about 1%, or preferably non-existent.

With reference to FIG. 4A, in some embodiments, the scintillation lightgenerated by the scintillator materials disposed in the lumens of themicrocapillary structures can be detected by an optical imager that isoptically coupled to the distal (or proximal) ends of the microcapillarystructures, where the distal (or proximal) ends provide exit aperturesthrough which the light can exit the microcapillary structures. By wayof example, in this embodiment, an optical imager 400 is in the form ofa CCD (charge coupled device) array that includes a two-dimensionalarray of optical image sensor elements where each of the optical imagesensor elements is optically coupled to the distal end of one of themicrocapillary structures to receive the light exiting thatmicrocapillary structure. In other words, in this embodiment there is aone-to-one relationship between the microcapillary structures and theoptical image sensor elements. Each of the optical image sensor elementscan generate one or more electrical signals in response to the detectionof the light incident thereon such that the combination of theelectrical signals generated by the image sensor elements provides imagedata for constructing a two-dimensional image of the radiation incidenton the radiation detector. In other words, each pixel of the imagecorresponds to the scintillator radiation generated by the scintillatormaterial associated with one of the microcapillary structures.

In other embodiments, multiple optical imagers can be optically coupledto multiple facets of a radiation detector according to the presentteachings to capture and detect scintillation radiation exiting thosefacets. By way of illustration, FIG. 4B shows a radiation detectorsystem having a radiation detector 100 and three optical imagers 400a/400 b/400 c, which are optically coupled to three facets of theradiation detector to receive and detect scintillation radiation exitingthose facets. In some embodiments, based on radiation detection signalsfrom the multiple facets, the position of interaction of the radiationcan be determined, which can then be used in enhancing (augmenting) theinformation obtained from the detector. As an example, determination ofthe depth of interaction of the incident radiation within theradiation-detecting material can improve timing jitter in positronemission tomography applications, thus resulting in images exhibitingbetter signal-to-noise (S/N) ratios.

In this embodiment, the scintillator material of each microcapillarystructure is substantially optically isolated from the scintillatormaterial disposed in an adjacent microcapillary structure. For example,in embodiments, the index of refraction of the material forming theperipheral walls of the microcapillary structures at the frequencycorresponding to the scintillation radiation is sufficiently lower thanthe respective index of refraction of the scintillator material suchthat the light rays generated in the scintillator material (or at leastthe majority of those light rays) undergo multiple total internalreflections as they are incident on the interface between thescintillator material and the peripheral wall of a microcapillarystructure.

As shown schematically in FIG. 5A, in some other embodiments the innersurface of the microcapillaries (or at least a portion thereof) iscoated with a reflective layer, e.g., a thin metallic layer, an oxidelayer, or a Teflon layer 500, e.g., a gold layer with a thickness in arange of about 10 nm to about 100 nm, so as to reflect the lightgenerated by the scintillator material so as to trap the light rays (orat least a majority thereof) within the microcapillary structure andinhibit their leakage into adjacent microcapillary structure(s). In yetother embodiments, the microcapillaries may be formed of a metal (e.g.,Pb or W), which can reflect the light generated by the scintillatormaterial.

In some embodiments, instead of or in addition to the reflective layer,an inner coating surface layer can be deposited on an inner surface ofthe microcapillary channels to enhance the radiation detectionperformance of the detector. For example, as shown schematically in FIG.5B, in addition to the reflective layer 500, such a layer 501 can be a⁶LiF (lithium fluoride enriched with lithium-6) layer coating an innersurface (or at least a portion of an inner surface) of themicrocapillary channels to enable high efficiency thermal neutrondetection. In other embodiments, the coating layer 501 can be formed onan inner wall of the microcapillary structures without the reflectivelayer 500. Such a coating can work synergistically with the scintillatormaterial within the lumens of the microcapillary structures to enhancethe detection efficiency of the radiation detector.

Further, in some embodiments, the inner walls of the microcapillariescan be coated with a wavelength-shifting material to convert a lowerwavelength scintillation light generated by the scintillator materialwithin the microcapillary to a higher wavelength light, resulting in amore efficient detection of the light using CMOS or CCD backplane orstate-of-the art photodetectors such as silicon photomultipliers.

For example, as shown schematically in FIG. 5C, such a coating 502 canabsorb the scintillation radiation generated by a scintillator materialwithin a microcapillary structure and emit radiation at a longerwavelength, e.g., a longer wavelength that can be more efficientlydetected by an optical imager that is optically coupled to the radiationdetector. For example, in one embodiment, the scintillation radiationmay have a wavelength of about 300 nm and the longer-wavelengthradiation that is emitted by the coating material may have a wavelengthof about 400 nm.

By way of example, such a wavelength-shifting coating (herein alsoreferred to as wavelength shifter (WLS)) can be formed on the innerwalls of the microcapillaries using vapor deposition of WLS materials,such as 1,1,4,4 Tetraphenyl Butadiene (TPB). By way of another example,the wavelength-shifting coating can be formed via solution deposition ofWLS, such as CsPbBr3 quantum dots, on the inner walls of themicrocapillaries.

The trapping of the light rays within the microcapillary structures caninhibit, and preferably prevent, their leakage into adjacentmicrocapillary structures and hence advantageously allow configuring theradiation detector such that the thickness of the scintillator materialcan be made sufficiently large to enhance the detection of the incidentradiation entering a microcapillary structured detector architecture,thereby increasing the detector's efficiency, while ensuring that theradiation detector would exhibit a high spatial resolution. In otherwords, in absence of such microcapillary structures, increasing thethickness of a scintillator material of a radiation detector can lead toa degradation of the radiation detector's spatial resolution due toisotropic propagation of the light generated by the scintillatormaterial. In contrast, in a microcapillary structured radiation detectoraccording to the present teachings, the light generated by thescintillator material within a microcapillary structure is substantiallytrapped within that microcapillary structure. As a result, thickerscintillator materials may be employed in a radiation detector accordingto various embodiments while ensuring that the radiation detectorexhibits a high spatial resolution.

In some embodiments, the spatial resolution of the radiation detectorcan be characterized by its modulation transfer function (MTF). As knownin the art, an MTF provides a quantitative measure of the spatialfrequency response of an imaging system. In some embodiments, aradiation detector according to the present teachings can exhibit an MTFof at least about 5%, e.g., in a range of about 5% to about 100%, forspatial frequencies in a range of zero to about 8 1p/mm (line pairs permillimeter) for detection of any of X-ray, γ-ray radiation, or neutrons.

With reference to FIG. 6A, in some embodiments, a radiation detector 600according to the present teachings can include multiple layers 602, 604of microcapillary structures, wherein the layers are stacked relative toone another. In this embodiment, the radiation detector layers 602, 604are vertically stacked relative to one another while in otherembodiments, such radiation detector layers can be stacked in any otherdesired orientation (e.g., horizontal orientation). In some embodiments,the radiation detector layers are configured to preferentially detectthe same radiation modality (e.g., γ-ray radiation). In some suchembodiments, the radiation that may pass through one layer without beingdetected could be detected as it passes through an adjacent layer,thereby increasing the detection efficiency of the radiation detector.

In some embodiments, multiple types of radiation (herein also referredto as radiation modalities) can be detected by the multiple layers. Byway of example, one layer of the microcapillary structures can beconfigured to detect γ radiation while another layer of themicrocapillary structures may be configured to detect thermal neutrons.For example, in such an embodiment, the scintillator material that ismore suitable for the detection of γ radiation can be, withoutlimitation, any of CsI, NaI, LaBr₃, SrI₂, CeBr₃, or combinations thereofand the scintillator material that is more suitable for the detection ofthermal neutrons can be any of ⁶LiF/ZnS, CLLB, CLYC, Li-glass, orcombinations thereof.

Further, in some embodiments, one layer of the multi-layermicrocapillary structures can be configured to provide preferentialdetection of incident radiation in different energy regimes, e.g.,similar to Phoswich scintillator configurations. For example, in somesuch embodiments, all of the layers of the microcapillary structures canbe configured for the detection of the γ radiation, but with differentlayers being configured for preferential detection of the γ radiation indifferent energy ranges. Such embodiments can be implemented byutilizing different scintillator materials and/or combinations thereof.

By way of example, in one implementation such a radiation detector caninclude two stacked layers of microcapillary structures, where one layer(e.g., the lower layer 602 in FIG. 6A) is configured for the detectionof γ radiation in a lower energy regime (e.g., γ rays having an energyin a range of about 1 keV to about 100 keV) and the other layer (e.g.,the upper layer 604 in FIG. 6A) is configured for the detection of γradiation in a higher energy regime (e.g., γ rays having an energy in arange of about 1 MeV to about 10 MeV). It should be understood that insome embodiments, the number of layers of the microcapillary structurescan be more than two, e.g., the number of layers can be in a range of 2to about 20, or more.

Further, in some embodiments, a plurality of layers can be configured topreferentially detect one type of incident radiation in different energyregimes and a plurality of other layers can be configured topreferentially detect another type of incident radiation in differentenergy regimes. By way of example, two tandem stacked layers can beconfigured to detect γ rays with one layer being configured forpreferential detection of the γ rays in a low energy regime (e.g.,energies in a range of about 1keV to about 100 keV) and the other layerbeing configured for preferential detection of the γ rays in a higherenergy regime (e.g., energies in a range of about 1 MeV to about 10MeV). Two other tandem stacked layers can in turn be configured todetect thermal neutrons, with one layer preferentially detecting thermalneutrons in one energy regime (e.g., in an energy regime of about 26meV)) and another layer preferentially detecting fast neutrons inanother energy regime (e.g., in an energy regime in a range of about 1to about 10 MeV).

In some embodiments, a radiation detector can include a single layer ofmicrocapillary channels in which the scintillator material in some ofthe microcapillary channels can be different than the scintillatormaterial in some of the other microcapillary channels to allow, e.g.,the detection of two or more different radiation modalities and/or toprovide different types of radiation detection information.

By way of example, FIG. 6B schematically shows an example of such aradiation detector 605 having a plurality of microcapillaries 607, eachof which has a hexagonal cross-sectional shape. A subset 607 a of thesemicrocapillaries are filled with a scintillator material (e.g.,scintillating plastic) that is suitable for the detection of X-rays andanother subset 607 b of the microcapillaries are filled with ascintillator material (e.g., organic glass scintillator) that issuitable for the detection of neutrons. While in this embodiment eachsubset constitutes 50% of the total number of the microcapillaries, inother embodiments, the number of microcapillaries in one subset may bemore than the number of microcapillaries in another subset. Further,more than two subsets of microcapillaries may be employed. For example,the number of subsets can range from 2 to about 20.

In some embodiments, one subset of the microcapillaries can beconfigured to provide information regarding the energy of the detectedradiation while another subset of the microcapillaries can be configuredto provide information regarding the timing of the detection of theincident radiation. By way of example, in some implementations, a subsetof the microcapillaries can be filled with a high-Z scintillatormaterial (such as CsI) to provide gamma energy information while anothersubset of the microcapillaries can be filled with a low-Z, but ultrafastscintillator material, to provide timing information.

The microcapillaries of the two subsets can be juxtaposed relative toone another in a variety of different ways, e.g., depending on aparticular application. For example, in this embodiment, themicrocapillaries of the two subsets are positioned as alternating rowsrelative to one another.

FIG. 6C shows another example of a radiation detector 610 according tothe present teachings, which similar to the previous embodiment,includes two subsets 612 a and 612 b of microcapillaries, where themicrocapillaries in the subset 612 a are filled with a scintillatormaterial that is suitable for the detection of X-rays and themicrocapillaries in the subset 612 b are filled with a scintillatormaterial that is suitable for the detection of thermal neutrons. In thisexample, the microcapillaries of the two subsets are arranged in analternating fashion relative to one another such that they form acheckerboard pattern.

Similar to the previous embodiments, an optical imager (e.g., CMOS orCCD backplanes or state-of-the-art photodetectors such as siliconphotomultipliers), not shown in this figure, can be optically coupled tothe microcapillary structures of the last layer to detect the lightgenerated by the scintillator materials disposed in the microcapillarystructures.

Semiconductor radiation detectors

In other embodiments, radiation detectors are disclosed, which include aplurality of microcapillary structures, such as those discussed above,having inner lumens that are partially, or fully, filled with asemiconductor material for detecting incident radiation. For example,with reference to FIGS. 7A and 7B, similar to the previous embodiment,such a radiation detector 700 includes a plurality of independentradiation sensing modules 702 (herein also referred to as radiationsensing elements or radiation detecting modules or radiation detectingelements, or simply sensing elements or detecting elements). Similar tothe previous embodiment, the plurality of sensing modules 702 arearranged relative to one another to collectively allow the detection ofincident radiation.

Similar to the previous embodiment, each radiation sensing module 702includes a microcapillary structure 704 that extends from a proximal end(PE) to a distal end (DE) along a longitudinal axis (LA), where theproximal and distal ends include apertures 704 a/704 b through which, insome embodiments, the electric charges generated in the semiconductor inresponse to the detection of incident radiation can be collected.

Again, similar to the previous embodiment, each microcapillary structure704 includes a peripheral wall 706 that surrounds an inner lumen 708,where the inner lumen is filled with a semiconducting material 710. Inthis embodiment the semiconducting material fills the entire volume ofthe lumen of each of the microcapillary structures from its proximal endto its distal end. In other embodiments the semiconducting material maypartially fill the inner lumen of one or more of the microcapillarystructures. In this embodiment, the peripheral wall 706 of themicrocapillary structure includes six facets that are positioned at anangle relative to one another such that the microcapillary structureexhibits a hexagonal cross-sectional shape in a plane perpendicular toits longitudinal axis.

In this embodiment, each of the radiation sensing elements includes apair of electrically conductive electrodes for collecting electriccharges generated in the semiconducting material (i.e., electron-holepairs) in response to the detection of incident radiation. As shownschematically in FIG. 7D, in this embodiment the conducting electrodesare implemented as a pair of metallic coatings disposed on an innersurface of each of the microcapillary structures with insulating gaps711 a/711 b separating the electrodes (e.g., the insulating gaps may beformed by the material of the peripheral wall of the microcapillarystructure, such as glass, quartz, PTFE).

The incident radiation can enter each of the microcapillary structures,such as the microcapillary structure 704 depicted in FIG. 7B, via any ofits peripheral walls and/or its proximal and distal apertures tointeract with the semiconducting material in that microcapillarystructure. The detection of the incident radiation by the semiconductingmaterial (e.g., the semiconducting material 710 shown schematically inFIG. 7C) within the microcapillary structure can result in thegeneration of electric charges (electron-hole pairs) within thesemiconducting material. Without being limited to any particular theory,the radiation incident on the semiconducting material within amicrocapillary structure can generate electron-hole pairs via excitationof electrons from a valence band of the semiconducting material to itsconduction band.

The electron-hole pairs can be collected by the opposed electrodes(cathode and anode) incorporated in the microcapillary structure togenerate one or more electrical signals indicative of the detection ofthe incident radiation. The electrical signals generated by theradiation detecting elements can be processed by electrical circuitry,e.g., an ASIC (application specific integrated circuit), in a mannerknown in the art as informed by the present teachings to generate animage of the incident radiation.

In some embodiments, the pair of conductive electrodes for collectingelectric charges generated in each of the radiation detecting elementscan be coupled to the proximal and distal ends of the radiationdetecting elements. FIG. 7E schematically depicts an example of such aradiation detector 714 that includes a plurality of radiation detectingelements 716, each of which is formed by filling a microcapillary with asemiconductor material in a manner described herein.

A pair of electrically conductive electrodes 718 a/718 b (anode andcathode) are coupled to the proximal and distal ends of each radiationdetecting element to collect electrical charges (electro-hole pairs)generated within the radiation-detecting material. The charges collectedat each of the electrodes 718 a/718 b can generate electrical signalsthat are received, respectively, by charge processing electronics analogor digital circuitries 720 a/720 b that can analyze the signals in amanner known in the art to determine, for each of the radiation detectorelements giving rise to the anode/cathode signals, the energy of theincident radiation and the timing of the signal.

Such data generated by the charge processing electronics analog ordigital circuitry 720 is received by an imaging interface 722 that isconfigured to utilize that data to generate an image of the incidentradiation. The charge processing electronics analog or digital circuitry720 and the imaging interface 722 can be implemented using knowntechniques in the art as informed by the present teachings.

In some embodiments, using the cathode and the anode signals generatedin response to the detection of incident radiation (e.g., γ radiation),the position of radiation interaction within the depth of thesemiconductor can be estimated. For example, the difference between thetiming of the electrical signals generated at the anode and the cathodeelectrodes in response to the detection of incident radiation can beemployed to determine the location of charge generation within thesemiconductor. Computational techniques known in the art, as informed bythe present teachings, can be employed to operate on the timing of theelectrical signals generated at the anode and the cathode electrodes toinfer the location of the charge generation within the semiconductormaterial. By way of illustration, an example of such computationaltechniques is provided in an article titled “Improved resolution for 3-Dposition sensitive CdZnTe spectrometers,” published in IEEE Transactionson Nuclear Science, Volume 51, Issue 5, Part 1, Oct. 2004, which isherein incorporated by reference in its entirety.

Based on this estimation of the position of the interaction of theincident radiation within the depth of the semiconductor, a correctionfactor can be calculated and applied to the energy spectra obtained fromthe electrical signals generated in response to the detection of theincident radiation in the semiconductor, resulting in betteridentification of the incoming radiation, as required by manyapplications such as radioisotope identifier equipment used for homelandsecurity applications.

In some embodiments, a radiation detector according to the presentteachings is capable of providing a high spatial resolution asdetermined by the microcapillary pitch and high energy resolution asprovided by the depth correction simultaneously.

A variety of semiconducting materials can be employed in the practice ofthe present teachings. Some examples of suitable semiconductingmaterials include, without limitation, elemental semiconductors, such assilicon, compound semiconductors, such as Cadmium Zinc Telluride,Thallium Bromide, Mercuric Iodide, Cesium Lead Bromide, GalliumArsenide, organic as well as organic-inorganic hybrid semiconductors,such as Methylammonium Lead Iodide, and Methylammonium Lead Bromide.

The walls of the microcapillary structures can be formed of a variety ofmaterials, such as those listed above in connection with the previousembodiment, including, without limitation, glass, quartz, metals (e.g.,Pb, W), plastic materials (e.g., PTFE).

In some embodiments, the semiconducting materials in the inner lumens ofthe microcapillary structures can have a single- or a poly- crystallinecomposition. In other embodiments, the semiconducting materials in theinner lumens of the microcapillary structures can be in the form of anamorphous semiconductor material.

In some embodiments, the inner surface of each of the microcapillarystructures that is at least partially filled with a semiconductingmaterial is coated, partially or fully, or can be formed of a highresistivity material, e.g., a material exhibiting a resistivity of about10¹⁶ Ωm, such as SiO₂ so as to reduce the total dark current exhibitedby the radiation-detecting element, thereby reducing the noise in thedata provided by the detector for constructing an image of the incidentradiation.

By way of example, FIGS. 8A and 8B schematically depict a microcapillarystructure 800 in which an SiO₂ layer 802 coats an inner surface of theperipheral wall of the microcapillary structure. By way of example, thethickness of the SiO₂ coating layer can be in a range of about 50 nm toabout 100 nm. In some embodiments, the SiO₂ layer can function as apassivating layer for reducing the dangling bonds at the surface of thesemiconductor material, thereby reducing the dark current associatedwith the semiconductor material. Although in this embodiment SiO₂ isemployed as the insulating layer, in other embodiments other suitableinsulating materials may be employed.

In some embodiments, a microcapillary structure can have both an innerelectrically insulating layer and an outer electrically conductive layercoating at least a portion of the inner surface of its peripheral wall.By way of example, FIGS. 8C and 8D schematically depict such amicrocapillary structure 804 in which an inner electrically insulatinglayer 806 and an outer electrically conductive layer 808 coat the innersurface of the peripheral wall of the microcapillary structure. By wayof example, the electrically insulating layer 806 can be an SiO₂ layerand the electrically conductive layer can be a gold layer. Theconductive layer can be held at a certain electric potential withrespect to the anode and the cathode (e.g., the anode and the cathode718 a/718 b depicted in FIG. 7E) to enhance the collection of theelectric charges generated in the semiconductor. Without being limitedto any particular theory, the electrical potential difference betweenthe conductive layer and the anode and cathode can generate an electricfield pattern within the semiconductor that can help with the collectionof the charged particles by the anode and the cathode. By way ofexample, and without limitation, in some implementations, a 100-nminsulating layer and a 50-nm electrically conducting layer can beemployed.

The combination of high thicknesses of the radiation-detecting materialsused in radiation detectors according to the present teachings togetherwith a high spatial resolution allows the use of such radiationdetectors in a variety of imaging applications. For example, radiationdetectors according to the present teachings can be used for neutronradiography, thereby providing detector solutions for X-ray and neutronmultimodal radiography. A variety of detector materials can be used inthe practice of the teachings.

Methods of Fabrication

With reference to the flow chart of FIG. 9 , one method of fabricating aradiation detector according to an embodiment of the present teachingsincludes dispersing one or more precursor materials including aradiation-detecting material or a precursor thereof into a plurality ofmicrocapillary channels and processing the precursor materials to causethe formation of radiation detecting elements within the microcapillarychannels so as to generate a plurality of independent radiation sensingelements each of which is associated with one of the microcapillarychannels.

By way example, in some embodiments, the precursor materials can becrystallized to form single or polycrystalline radiation detectingelements. By way of example, solution-based techniques may be employedfor causing the crystallization of the precursor material(s). Forexample, the crystallization of the precursor materials can be achievedvia using solvent evaporation techniques, which can include directionalevaporation of the solvent facilitated by changing the temperature orthe pressure of the fabrication atmosphere (e.g., via application of avacuum).

In some embodiments, the crystallization of the precursor materials canbe achieved using antisolvent-assisted crystallization where, forexample, the antisolvent is introduced to the fabrication atmosphere ata certain rate and volume, thereby initiating and continuingcrystallization of the sensor elements inside the microcapillaries.

In some embodiments, the crystallization of the precursor materials canbe achieved via inverse temperature crystallization. For example, byincreasing the temperature of the fabrication atmosphere at a controlledrate, the solubility of the crystal in its supersaturated solution isdecreased, resulting in seed crystallization inside themicrocapillaries. With time and further changes in the temperature, theseed crystals grow and fill up the microcapillaries.

In some embodiments, the crystallization of the precursor materials caninclude the use of polymerization techniques. Some examples of suchpolymerization techniques include, without limitation, condensationpolymerization and addition polymerization. The polymerization processmay also include temperature and pressure-related fabrication steps.

In some embodiments, the crystallization of the precursor materials canbe achieved using melt-based techniques.

In some embodiments, the crystallization of the precursor materials canbe achieved using directional gradient temperature freezing. In thistechnique, a directional temperature gradient is applied to a substrateor a fabrication atmosphere to nucleate and grow the crystalline sensormaterials inside the microcapillaries. For proper nucleation,geometrically modified microcapillary structures can be used. As anexample, the microcapillaries can have a closed pointed conical end(See, e.g., FIG. 1D) to initiate the crystal nucleation. These nucleiwill grow based on the directional temperature gradient imposedexternally. Depending on the application, the pointed part of themicrocapillary can be removed before using the resulting microcapillarystructures as radiation detecting elements.

In some embodiments, the crystallization of the precursor materials canbe achieved using heat exchanger method growth. In such a method, thetemperature of the substrate is actively varied over time to initiateand propagate single crystalline, or polycrystalline growth of thesensor elements inside the microcapillaries. Such a technique can alsobe utilized to cause the precursor materials to form an amorphouscomposition functioning as the sensor elements.

In some embodiments, the crystallization of the precursor materials canbe achieved using a gas-assisted crystal growth technique. In thisprocess, a gas stream of a certain composition is flowed in the vicinityof the substrate, thereby inducing seed nucleation and facilitatingcrystal growth inside the microcapillaries.

In some embodiments, the crystallization of the precursor materials canbe achieved using thermal quenching. In such a technique, thetemperature of the substrate or the atmosphere around it is changedquickly (known as quenching in the art), thereby including crystalnucleation and growth.

In some embodiments, physical vapor deposition techniques can beutilized to fill the microcapillaries with the precursor materials. Insome embodiments, the microcapillaries can be filled with the precursormaterials using thermal evaporation. In such a technique, the precursormaterials can be vaporized at a high temperature and deposited on themicrocapillary walls so as to slowly fill up the microcapillaries.

In some embodiments, sputtering techniques can be utilized for fillingthe microcapillaries with precursor materials. In such techniques, theprecursor materials are sputtered and deposited on the microcapillarywalls so as to slowly fill up the microcapillaries.

In some embodiments, atomic layer deposition techniques can be utilizedfor filling the microcapillaries with the precursor materials. In suchtechniques, the precursor materials can be atomically deposited on thewalls of the microcapillaries so as to slowly fill up with themicrocapillaries.

In some embodiments, chemical vapor deposition techniques can beemployed to fill the microcapillaries with the precursor materials.

The following examples are provided for further elucidation of variousaspects of the present teachings and are not intended to necessarilyspecify the optimal ways of fabricating radiation detectors according tothe present teachings or optimal results that may be obtained using suchradiation detectors for detecting incident radiation.

Examples

X-ray imaging is the most common and widely used diagnostic techniquethat spans numerous fields. X-rays interact with the atomic electronsresulting in higher absorption cross-sections for higher atomic numberelements depending on the overall electron density distribution of theobject. X-ray radiography is currently performed primarily using directand indirect techniques, which involve the detection of charge carriersand photons generated by the X-rays, respectively.

Indirect flat panel X-ray imagers (FPXIs) with scintillating layers(such as commercially available microcolumnar CsI and Gd₂O₂S) have highdetective quantum efficiency (DQE) and are the preferred detectors forall hard X-ray imaging applications. However, to limit the spreading ofthe scintillation light, the thicknesses of these sensors are limited toabout —500 μm. These sensors provide decent spatial resolutions withmodulation transfer function (MTF) values around 30% at 2 1 p/mm, butthe lower thickness limits the detector sensitivity, resulting in higherX-ray dose requirements. Direct detectors are good candidates forachieving higher spatial resolutions. However, charge trapping anddefect-related challenges lower the sensitivity of these detectorssignificantly. Due to their lower atomic numbers, the most successfullarge area direct detectors such as amorphous selenium (a-Se) andsilicon have low efficiencies for higher X-ray energies.

Spatial resolution is an extremely important factor for X-ray imagingthat helps users distinguish between two adjacent features. A detectorwith high MTF, for example, can reliably detect a micron-scale cancerouslesion or a mm-scale fracture in a gas pipeline with high levels ofconfidence. While the trend of the imaging industry is shifting towardsfeature recognition using artificial intelligence, higher spatialresolution in radiography images significantly enhances the detectionprobabilities of subtle features such as pulmonary nodules using theneural network deep learning models.

In addition to spatial resolution, the indirect detectors must providehigh enough contrast, be manufacturable in large areas (>10 cm×10 cm),have a fast decay time, and have a low afterglow.

An exemplary detector was fabricated based on the present teachings asdiscussed in more detail below. The exemplary fabricated detector canprovide an excellent solution for high spatial resolution X-rayradiography. The detector included a solution-processabletwo-dimensional (2D) hybrid perovskite single-crystal scintillator,lithium-alloyed phenethylammonium lead bromide (PEALPB) incorporatedinto a glass microcapillary array.

In terms of crystal structure, hybrid (containing organic and inorganicconstituents) perovskite scintillators can be classified asthree-dimensional (3D) and two-dimensional (2D). Although the 3Dperovskite scintillators with lower exciton binding energy (tens of meV)have been shown to provide excellent X-ray scintillator response, the 2Dperovskite scintillators have the potential for providing higher lightyield and faster decay due to their higher exciton binding energy(hundreds of meV). The 3D lead halide perovskites can be transformedinto a 2D one by introducing a long alkyl chain or a bulky organiccation. PEALPB belongs to the 2D family, where the alternatinginorganic/organic layers effectively confine the exciton inside theinorganic layer generating scintillation in response to X-rays, fastneutrons, and alpha particles that are released as a byproduct ofthermal neutron absorption by Li. Li-doping provides a unique benefitfor perovskite materials. Even though the solution-processed hybridperovskites have demonstrated excellent performance in manyapplications, a high concentration of trap states with a density of10¹⁵-10¹⁶ cm⁻³ still exists, resulting in nonradiative recombination.

It has been experimentally verified that this deleterious feature can besignificantly reduced when the lattice is doped with high concentrationsof Li. It is possible to synthesize 2D scintillators with highconcentrations of ⁶Li due to the small size of the Li-ion relative tothe large unit cell of 2D materials. Li-alloying also broadens theradioluminescence emission spectra of PEALPB, with its maximum at 436nm. Li-doping also substantially increases the light yield of the PEALPBscintillators.

In this example, the light yield of free-standing single-crystal PEALPBsensors was found to be around 18,700±1200 ph/MeV as measured using¹³⁷Cs gamma source. The fabricated sensor of this example successfullydemonstrates the high spatial resolution limits that can be achieved forX-ray imaging using the present teachings. In addition, the presence of⁶Li provides a large capture cross-section for the detection of thermalneutrons, while the high concentration of hydrogen (24 hydrogenatoms/molecule) enables the detection of fast neutrons.

Thus, by adjusting the content of ⁶Li in the matrix, these detectors canalso be tuned to detect neutrons over a wide range of energies. Theresults show the neutron detection capabilities are provided furtherbelow. The spatial resolution of the exemplary detectors fabricated inaccordance with the present teachings with thicknesses as high as1200 μmwas measured to be better or comparable to the state-of-the-art directand indirect detectors with much lower thicknesses. The decay timeconstant of the PEALPB 2D perovskite detector was measured to be about11-24 ns, and its afterglow was an order of magnitude lower than themodern industry-standard CsI scintillators.

Thus, compared to the CsI scintillator-based detectors, the maximumcount rate of detectors based on PEALPB can be expected to beappreciably higher. Although no specific radiation hardness studies havebeen done for PEALPB, in general, the radiation tolerance of the 2Dperovskites has been shown to be very high, which makes them appropriatefor high flux X-ray synchrotron beamline and industrial applications.

A high detection efficiency is needed to enable high-energy X-rayimaging. For all known scintillators, this can be achieved by the use ofthick films of the order of several millimeters. For example, for 50%attenuation of 150 keV X-rays, CsI detectors require a thickness of 2.1mm. Such film thicknesses, however, are not conducive to high spatialresolution imaging, as the photons generated in the film propagateisotropically and impinge on a multitude of pixels on the imaging chipresulting in blurred images. To overcome this issue, in this example,microcapillary plates with pore sizes between 20 μm and 100 μm wereemployed.

Specifically, 100 and 20-micron pore diameter microcapillary plates werefilled with single-crystalline PEALPB perovskite scintillator withsimilar X-ray attenuation coefficients compared to CsI (e.g. 1.9 vs. 1.8cm²/g at 100 keV) and an X-ray imager using this sensor wasdemonstrated. FIGS. 10A and 10B summarize the overall approach for theproduction of these microcapillary-based detectors. FIG. 10C shows amagnified fluorescence view of the microcapillaries containing thesingle crystals of PEALPB. The back image in FIG. 10C shows a 2 cm×2cm×1.2 mm microcapillary plate scintillating under UV irradiation. Thearriving X-rays from the source ionize the scintillator material in themicrocapillary, producing photons that emanate isotropically. The indexof refraction of PEALPB is appreciably higher (— 1.9-2.1) than that ofthe microcapillary walls made from silica (— 1.5). The refractive indexof the PEALPB scintillators was measured using a refractive index meter.The photons undergo nearly complete internal reflections along the glasscapillary before they leave the detector to enter the photon collectingphotodetectors.

Geant4 simulations were used to assess the effectiveness ofmicrocapillaries to achieve a high spatial resolution. A Geant4 model ofa high-density array of 29,000 hexagonal PEALPB detectors wasconstructed (FIGS. 11A-11C). The faceplate was placed on a siliconimager consisting of 400×400 square pixels of 50 μm on a side. Acircular pattern of radiation, either 32 keV hard X-rays (and 25 meVthermal neutrons) was directed at the faceplate from above to assess theability of the design to provide good imaging resolution. Energydeposited by the radiation in PEALPB generated optical photons thatscattered throughout the faceplate. However, as shown in FIGS. 12A and12B, the difference in refractive index between PEALPB and glass tendedto confine the photons to the hexagonal microcapillary, resulting inmost photons being collected directly beneath the point of interaction.

These simulations show that radiation detectors according to the presentteachings can provide a very high spatial resolution detectors.

In addition to X-rays, ⁶Li-alloyed Phenethylammonium lead bromide(PEALPB) is also responsive to neutrons. The thermal neutrons interactwith the ⁶Li in PEALPB, and an alpha and triton are produced from eachinteraction. These charged particles then ionize the scintillatorresulting in the generation of photons which, like those generated byX-rays, undergo near-complete internal reflection and leave thedetector. For fast neutrons with energy En primarily undergo elasticscattering with the hydrogen in the PEAPLB and produce recoil protonswith energy, E_(p)=E_(n) cos 2θ,θ being the scattering angle. Theseprotons ionize the scintillator and produce the photons that are thendetected by the photodetectors.

The device architecture shown in FIG. 13 was used for performing GEANT4simulation results. The fast neutron detection efficiency of themicrocapillary detector was evaluated by Geant4 Monte Carlo simulations.

FIG. 14 shows the calculated number of photons collected by the imagerafter firing fast neutrons with an energy of 2.5 MeV, to represent aDeuteron-Deuteron (DD) neutron source, and 14.1 MeV, to represent a DTneutron source, at a series of PEALPB detectors with varying thicknessespractical for radiography. As the thickness of the film increases, morefast neutrons are captured resulting in an increase in the number ofphotons captured by the imager. The performance of these devices wascompared to the performance of stilbene devices of the same thickness(red), and it was observed that PEALPB devices, especially at lowerthicknesses, are competitive with stilbene for fast neutron detection.

The thermal neutron results are shown in FIGS. 15A and 15B. The lightgenerated by the thermal neutron sensitive PEALPB was confined to themicrocapillaries due to total internal reflection resulting in a highspatial resolution.

The neutron detection performance of these detectors in terms of neutronsensitivity exceeded that of the commercial sensors used for neutronradiography (See, e.g., FIGS. 16 and 17 ). For X-ray imaging, a camerawas constructed using the 2 cm×2 cm microcapillary plates with themicrocapillaries filled with single crystals of PEALPB, as shown inFIGS. 10A and 10B. A microcapillary diameter of 20 μm and a CMOS chippixel pitch of 3.75 μm was used to construct this high spatialresolution indirect camera.

FIGS. 18A and 18B show the PEALPB detector and the CMOS chip, which wereused to construct an image detector (herein also referred to as acamera) according to an embodiment of the present teachings, under UVirradiation. This camera was placed in line with a microfocus X-raysource, and the imaging objects were placed on an XYZ stage in between.

The properties of the CMOS chip used for fabricating the X-ray imagingcamera are presented in Table 1 below:

TABLE 1 Number of pixels 4096 × 3000 Optical format 17.5 mm Pixel size3.45 microns × 3.45 microns Full well capacity >10,650 e Dynamic range71 dB

First, the uniformity of the background was measured without any imagingobject positioned between the camera and the X-ray source. Thebackground image acquired using 90 kV X-ray is shown in FIG. 19 . Sevenregions of interests (ROIs) with 200×200 pixels were used to perform theuniformity analysis. The uniformity of the background image was foundwithin 0.056% with about 4% noise. The detailed ROI statistics for theseregions are provided in Table 2 below:

TABLE 2 Standard ROI Mean Deviation 1 157.19 47.82 2 156.86 47.92 3157.76 48.98 4 156.02 46.47 5 156.24 47.81 6 155.43 46.93 7 157.45 48.58

FIGS. 20A and 20B show the images of an X-ray resolution target takenusing the PEALPB camera and a Timepix camera with a silicon sensor. Theexcellent spatial resolution of the PEALPB camera is evident. Therelative contrast measured on the raw image for PEALPB at the lowestfrequency of the X-ray resolution target gives an average of 491.7compared to 531.8 for the Si detector. The signal-to-noise ratio (SNR)for this area is measured to be 78. FIGS. 21A and 21B show the X-rayimage of a mini USB drive circuit. The tiniest features were wellresolved.

The MTF of this detector was calculated using the slanted edgetechnique. FIG. 22 shows the MTF versus spatial frequency plot derivedfrom the PEALPB camera. This figure also summarizes the MTF values fordifferent other direct and indirect sensors. This comparison has notbeen done under the same experimental conditions (such as X-ray dose orenergy). However, as these are the best-achieved values for these sensormaterials, FIG. 22 clearly shows the enhanced spatial resolution of themicrocapillary-based PEALPB detectors over the other state-of-the-artsensors.

For the best indirect sensor materials such as micro-columnar CsI or thenewly discovered CsCu₂I₃ with micro-columnar structures, the MTF valuesdecrease sharply with film thicknesses. In addition, for semiconductordetectors, increasing the thickness of the detector enhances chargetrapping and detector noise resulting in reduced detector sensitivityand bandwidth.

In contrast, this example shows that with the microcapillary-baseddetector structure, even with thicknesses as high as 1.2 mm, thedetector spatial resolution, as well as its sensitivity to X-rays, canbe simultaneously well maintained.

The best available spatial frequencies with 10% and 50% MTF fordifferent detectors are summarized in Table 3 below. Higher sensorthicknesses are necessary to increase the efficiency and sensitivity ofthe detectors. None of the existing technologies can provide a solutionfor fabricating detectors with higher thicknesses without adverselyaffecting the spatial resolution.

TABLE 3 Detector Spatial Spatial Thickness frequency frequency Detector(μm) at 10% MTF at 50% MTF PEALPB (this example) 1200 8.8 5.5Microcolumnar CsI 200 6 2.1 Pixelated 700 4.6 1.5 Microcolumnar CsIMicrocolumnar CsCu2I3 100 8.7 5.4 Timepix with Si 300 8.6 5.1 a-Se 25013 6.8 MAPBI3 230 10 4.1

The data in FIG. 22 also shows that the multimodal X&N detector based onPEALPB can provide high spatial resolution matching an ideal camera with100 μm pixels. The sinc function, defined

${{Sinc}{\left( {rf} \right) = \frac{S{{inc}\left( {r\pi f} \right)}}{r\pi f}}},$

where r and f represent the pixel pitch and spatial frequency,respectively, represents the theoretical limit of the MTF by assumingthat the pixel aperture is the only image blurring mechanism in theradiography camera.

The data in FIG. 22 shows that some degree of light sharing or leakagecan occur between each microcapillary and surrounding microcapillaries,resulting in some global average blurring imperfections in thedetector's response. The expected Nyquist frequency for 20 μmmicrocapillaries is 25 1p/mm. To reduce the blurring, microcapillarieswith extramural absorption were employed to further improve thedetector's spatial resolution and obtain a high MTF at the Nyquistfrequency. At 25 1p/mm, an MTF of 3.2% was obtained.

FIG. 23 shows the MTF plot for the microcapillary-based detector withextramural absorption layers made of opaque glass. It shows an excellentspatial resolution greater than that exhibited by any conventional X-raysensor. However, high X-ray doses were needed to generate these imageswhere the darkening effect from the extramural pattern requiredextensive correction, thus rendering the use of absorption layersunsuitable for low-dose X-ray imaging.

The use of a pixelated CMOS or α-Si:H back planes is expected to furtherimprove the spatial resolution of a detector according to the presentteachings beyond that shown in this example.

Those having ordinary skill in the art will appreciate that variouschanges to the above embodiments can be made without departing from thescope of the present teachings.

1.-104. (canceled)
 105. A radiation detector, comprising: a plurality ofmicrocapillary structures, wherein said microcapillary structures are atleast partially filled with a radiation detecting material so as toprovide a plurality of independent radiation sensing elements such thateach of the radiation sensing elements is associated with one of saidmicrocapillary structures for detecting incident radiation andgenerating one or more signals in response to the detection of theincident radiation.
 106. The radiation detector of claim 105, whereinsaid radiation detecting material has any of a single- and poly-crystalline structure.
 107. The radiation detector of claim 105, whereinsaid radiation detecting material has an amorphous structure.
 108. Theradiation detector of claim 105, wherein said radiation detectingmaterial comprises a first scintillator material configured to generatescintillation radiation in response to detection of the incidentradiation.
 109. The radiation detector of claim 108, wherein saidincident radiation comprises any of α, β, γ, X-ray and neutrons. 110.The radiation detector of claim 108, wherein said scintillator materialcomprises any of an organic, an inorganic and an organic-inorganichybrid scintillator material.
 111. The radiation detector of claim 110,wherein said organic-inorganic hybrid scintillator material comprisesany of OD, 1D, 2D or 3D perovskite material.
 112. The radiation detectorof claim 108, wherein said microcapillary structures are formed in asubstrate.
 113. The radiation detector of claim 112, wherein saidsubstrate comprises a second scintillator material.
 114. The radiationdetector of claim 113, wherein said second scintillator material isdifferent from said first scintillator material.
 115. The radiationdetector of claim 114, wherein said first and second scintillatormaterials are suitable for detection of different radiation modalities.116. The radiation detector of claim 105, wherein said substratecomprises a material exhibiting an index of refraction greater than anindex of refraction of said scintillator material at a frequencyassociated with the optical radiation such that the optical radiationgenerated in each of said sensing elements is substantially trappedwithin that sensing element via internal reflection at interfacesbetween said scintillator material and said substrate material.
 117. Theradiation detector of claim 105, wherein at least one of said channelscomprises a coating layer covering at least a portion of an innersurface thereof for enhancing photon generation in response to theincoming radiation and enhancing optical isolation between said at leastone channel and an adjacent channel.
 118. The radiation detector ofclaim 108, wherein at least one of said microcapillary structurescomprises a wavelength shifting material coating at least a portion ofan internal surface thereof.
 119. The radiation detector of claim 108,wherein said plurality of microcapillary structures comprises at leasttwo subsets having different scintillator materials.
 120. The radiationdetector of claim 108, wherein said plurality of radiation sensingelements are distributed in two or more stacked layers.
 121. Theradiation detector of claim 120, wherein the radiation sensing elementsassociated with at least two of said layers include differentscintillator materials.
 122. The radiation detector of claim 108,further comprising an optical imager optically coupled to saidindependent radiation sensing elements to receive the scintillationradiation to generate an image corresponding to the incident radiation.123. The radiation detector of claim 122, wherein said image exhibits amodulation transfer function (MTF) of at least 5% for detection of theincident radiation.
 124. The radiation detector of claim 105, whereinsaid radiation detecting material comprises a semiconductor material,wherein said semiconductor material is configured to generate electriccharges in response to detection of the incident radiation.
 125. Theradiation detector of claim 124, wherein each of said microcapillarystructures comprises a plurality of electrodes for collecting saidelectric charges generated by the semiconductor in response to detectionof the incident radiation.
 126. The radiation detector of claim 125,wherein the plurality of electrodes associated with each of saidmicrocapillary structures comprises an anode electrode and a cathodeelectrode electrically coupled to opposed ends of the microcapillarystructure.
 127. The radiation detector of claim 125, wherein each ofsaid plurality of electrodes comprises an electrically conductive layercoating at least a portion of an inner surface of a respective one ofsaid microcapillary structures and being in electrical contact with thesemiconductor material associated with that microcapillary structure.128. The radiation detector of claim 124, wherein at least one of saidmicrocapillary structures comprises a passivating, electricallyinsulating layer coating at least a portion of an inner surface thereoffor reducing dark current associated with the semiconductor material.129. The radiation detector of claim 124, wherein at least one of saidmicrocapillary structures comprises an inner electrically insulatinglayer and an outer electrically conductive layer coating at least aportion of an inner surface thereof.
 130. The radiation detector ofclaim 124, wherein said microcapillary structures are formed in asubstrate.
 131. The radiation detector of claim 130, wherein saidsubstrate comprises any of glass, polymer, ceramic, metal orsemiconductor material.
 132. The radiation detector of claim 124,wherein said semiconductor material comprises any of silicon, Ge,CdZnTe, CdTe, HgI₂, BiI₃, TIBr, CsPbBr₃, MAPbBr₃, MAPbI₃, FAMACs. 133.The radiation detector of claim 125, further comprising a detection andanalysis circuitry electrically coupled to said radiation detectingelements for receiving the electrical signals generated by theelectrodes of said radiation detecting elements and analyzing theelectrical signals to generate an image of the incident radiation. 134.The radiation detector of claim 133, wherein said radiation detector andsaid detection and analysis circuitry are configured such that saidimage exhibits a modulation transfer function (MTF) of at least 5% fordetection of said incident radiation.